From: Perry Holcomb <hpholcomb@yahoo.com>

Date: November 29, 2007 7:12:19 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Raising a heat issue

Hi to all,

This newbie even enjoys reading about the

heat/turbulence issue.

I'm a retired chemist, not a physicist or an engineer.

Common sense should tell you that its gonna be a

relationship between the OAT and the number of joules

involved and the base thermal stability of the air.

I may be wrong, but wouldn't thermal turbulence be

more of a problem at lower OATs from such

dew-defeating devices than at more moderate temps?

I'll pose another question.  How about other sources

of heat like the human body (that's been mentioned and

which is throwing off heat about the equivalent of a

100W incandescent), like equipment that isn't at

equilibrium with the OAT and is emitting heat to gain

same, and how about that heat-generating chip itself??

Wouldn't those be more of a factor at lower OATs re

generating thermal turbulence??

Interesting stuff, isn't it??  Is there a

thermodynamicist in the crowd??

Perry

--- Ray Byrne <ray@in4media.co.uk> wrote:

Hi Duane,

I've started using my dew heater strap and wonder

what effect it  

could possibly have on my planetary imaging efforts.

On my last  

outing I gave up after 4 hours of trying to image

Mars it was  

wobbling like a jelly. My friend Mick Hyde who lives

about a mile  

away and lives in similar surroundings managed to

take some great  

shots with the exact same gear minus the dew heating

but  

inconclusively about 30 minutes after I'd packed it

in for the night.

Any comments anyone?

On 29 Nov 2007, at 06:01, Duane wrote:

What about dew heater straps on scopes, will these

cause problems?  

I have a dew buster with

a temp sensor, which is supposed to keep things

just warm enough to  

keep dew off (if used

correctly), but I'm not sure. This is pretty

hi-res imagery, should  

i be taking greater

precautions against local heat turbulence?

ATB

Ray Byrne

in4media | graphic and website DESIGN

T: 01793 435704

W: http://www.in4media.co.uk

     ____________________________________________________________________________________

Get easy, one-click access to your favorites. 

Make Yahoo! your homepage.

http://www.yahoo.com/r/hs